The only correct sentence is: "¿A qué distancia está la playa?"
If you use "es" people will understand, but you're asking for a location, so the suitable verb is "estar".

For using "qué" instead of "a qué", you should ask another question:
- ¿Qué tan lejos está la playa?
- ¿Qué distancia hay de aquí a la playa? -> You might also find "¿qué distancia es de aquí a la playa?"; in that case, it's the distance what is referred to with the verb "es" and not the beach.
- ¿Qué tan lejos queda la playa? -> The verb "quedar" here, includes the idea of the distance travelled.

If the confusion comes from questions like: "¿Dónde es el correo?",
although you're apparently asking for a location, and the verb should be "estar", if you are trying to find the post office among many buildings, the idea of the question using "es" is rather "which of these buildings is the post office?"

Let me know if you still find it confusing.

Quote:

Originally Posted by BobRitter

Muchas maneras a decir la misma cosa. (Or "muchas maneras de decir lo mismo" without "cosa" -> With "cosa", you need to make a gender agreement with "la" and "misma".)

TodoComo siempre, gracias a todos por su ayuda.

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